<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            /*盒子的内容自动内减*/
            box-sizing: border-box;
        }

        .box {
            width: 400px;
            height: 100px;
            background-color: #f00;
            /*padding: 10px;*/
            padding-left: 40px;
            padding-top: 40px;
            border-top: 30px solid #000;
            /*margin: 0 auto;*/
            margin-left: 50px;
            /*margin-right: 50px;*/
            margin-top: 50px;
            /*margin-bottom: 50px;*/
            /*margin: 50px;*/
            /*margin: 50px 50px;*/
            /*margin: 50px 50px 50px;*/


        }
    </style>
</head>
<body>
<div class="box">123456</div>
<div class="box">6789</div>

</body>
</html>
